Effects Of The Revision On The Mental Ages Secured

The most important effect of the revision is to reduce the mental ages secured in
the lower ranges of the scale, and to raise considerably the mental ages above
10 or 11 years. This difference also obtains, though to a somewhat
smaller extent, between the Stanford revision and those of Goddard and
Kuhlmann.

For example, of 104 adult individuals testing by the Stanford revision
between 12 and 14 years, and who were therefore somewhat above the level
of feeble-mindedness as that term is usually defined, 50 per cent tested
below 12 years by the Goddard revision. That the dull and border-line
adults are so much more readily distinguished from the feeble-minded by
the Stanford revision than by other Binet series is due as much to the
addition of tests in the upper groups as to the relocation of existing
tests.

On the other hand, the Stanford revision causes young subjects to test
lower than any other version of the Binet scale. At 5 or 6 years the
mental ages secured by the Stanford revision average from 6 to 10 months
lower than other revisions yield.

The above differences are more significant than would at first appear.
An error of 10 months in the mental age of a 5-year-old is as serious as
an error of 20 months in the case of a 10-year-old. Stating the error in
terms of the intelligence quotient makes it more evident. Thus, an error
of 10 months in the mental age of a 5-year-old means an error of almost
15 per cent in the intelligence quotient. A scale which tests this much
too low would cause the child with a true intelligence quotient of 75
(which ordinarily means feeble-mindedness or border-line intelligence)
to test at 90, or only slightly below normal.

Three serious consequences came from the too great ease of the original
Binet scale at the lower end, and its too great difficulty at the upper
end:--

1. In young subjects the higher grades of mental deficiency were
overlooked, because the scale caused such subjects to test only a little
below normal.

2. The proportion of feeble-mindedness among adult subjects was greatly
overestimated, because subjects who were really of the 12- or 13-year
mental level could only earn a mental age of about 11 years.

3. Confusion resulted in efforts to trace the mental growth of either
feeble-minded or normal children. For example, by other versions of the
Binet scale an average 5-year-old will show an intelligence quotient
probably not far from 110 or 115; at 9, an intelligence quotient of
about 100; and at 14, an intelligence quotient of about 85 or 90.

By such a scale the true border-line case would test approximately as
follows:--

At age 5, 90 I Q (apparently not far below normal).
At age 9, 75 I Q (border-line).
At age 14, 65 I Q (moron deficiency).

On the other hand, re-tests of children by the Stanford revision have
been found to yield intelligence quotients almost identical with those
secured from two to four years earlier by the same tests. Those who
graded feeble-minded in the first test graded feeble-minded in the
second test: the dull remained dull, the average remained average, the
superior remained superior, and always in approximately the same
degree.[18]

[18] See "Some Problems relating to the Detection of Border-line Cases
of Mental Deficiency," by Lewis M. Terman and H. E. Knollin, in _Journal
of Psycho-Asthemes_, June, 1916.

It is unnecessary to emphasize further the importance of having an
intelligence scale which is equally accurate at all points. Absolute
perfection in this respect is not claimed for the Stanford revision, but
it is believed to be at least free from the more serious errors of other
Binet arrangements.